Re: [RFC PATCH v2] hw/display/tcx: Allow 64-bit accesses to framebuffer stippler and blitter

[Michael]

Hello,

since I wrote the NetBSD code in question, here are my 2 cent:

On Sat, 29 Aug 2020 08:41:43 -0700
Richard Henderson <richard.henderson@linaro.org> wrote:

> On 8/22/20 7:21 AM, Philippe Mathieu-Daudé wrote:
> > The S24/TCX datasheet is listed as "Unable to locate" on [1].

I don't have it either, but someone did a lot of reverse engineering
and gave me his notes. The hardware isn't that complicated, but quite
weird.

> > However the NetBSD revision 1.32 of the driver introduced
> > 64-bit accesses to the stippler and blitter [2]. It is safe
> > to assume these memory regions are 64-bit accessible.
> > QEMU implementation is 32-bit, so fill the 'impl' fields.

IIRC the real hardware *requires* 64bit accesses for stipple and
blitter operations to work. For stipples you write a 64bit word into
STIP space, the address defines where in the framebuffer you want to
draw, the data contain a 32bit bitmask, foreground colour and a ROP.
BLIT space works similarly, the 64bit word contains an offset were to
read pixels from, and how many you want to copy.

have fun
Michael